For image scanning systems/apparatuses, a scanned image is generally distorted, e.g., subjected to perceptive transformation, stretching-deformation, etc., in both a traditional flat-panel scanner and an advanced set-top curved-surface scanner. It is thus important to remove these distortions and correct the scanned image. In order to attain this object, it is crucial to obtain true corner points of the scanned image because these corner points are parameters of a document correction model.
When true corner points of a document are obtained in some of existing methods and/or detectors for detecting a corner point (e.g., a Harris technology to detect a corner point), such methods may suffer from low precision due to insufficient information available thereto.